The purpose of the lateral thrust control unit is to apply a lateral force onto the ship through the thrust-producing device, mostly a propeller, which is provided in the tunnels which are arranged transversely to the longitudinal axis of the watercraft, to thus increase the maneuverability of the watercraft. I have found that during a longitudinal and simultaneous lateral movement of the ship, an underpressure field is created on one wall of the ship and an overpressure field is created on the other wall of the ship, which pressure fields are directed opposite to the lateral thrust and which reduce the effect of the lateral thrust control unit.
For this reason, I have already suggested means in U.S. Pat. application Ser. No. 380,667, filed July 19, 1973, which means diminish the interfering pressure fields. These means consist of at least one pressure-compensating channel, which also extends from one sidewall of the watercraft to the other one and connects the areas of the opposite potentials. It is thereby of less importance whether or not the pressure-compensating channel or the pressure-compensating channels extend indeed from one sidewall of the watercraft to the other sidewall and open outwardly near the tunnel openings, even though this arrangement has been proven to be practically the most effective one. Instead, it is the diminishing of the pressure fields that is the most important. Moreoever, a pressure-compensating channel effects a smaller water jet deflection of the exiting jet of water and an additional impulse through the present passive flow, which has the same direction as the jet of water from the lateral thrust control unit. Thus, it is possible to provide, for example, one or several channels which connect the interfering pressure fields to a different area of opposite and lesser potential. Also, in principle, it does not matter which shape these pressure-compensating channels have.
The lateral thrust units can be provided in front or astern or several times, for example, in front and astern or in a different suitable manner on the watercraft.
The purpose of the invention is to construct the abovediscussed lateral thrust control units more effectively, in particular to concentrate the required structure in the available space, in particular for watercraft having a draught limitation which would bring about the danger of air being sucked into the tunnel when large diameters are used for the lateral thrust control unit. Individual units having a high output require the use of high voltage, which is not available in many cases or does not appear advantageous for various reaasons. Also, it may be that the use of high voltage is not desired.
The basic purpose of the invention is achieved by providing a lateral thrust control unit which includes a pair of tunnels having propulsion means therein. The units can thereby be used together or individually in both directions of travel. It is also possible to use the one tunnel of the pair as a stand-by unit in case of a failure of the waterdrive unit in the other tunnel. In this connection it must again be pointed out that the shape and path of the compensating channels is not important. Instead, the diminishing of the damaging pressure fields is the most important.
An effective double unit is obtained when closure devices for the compensating channels are remote controlled in a known manner. Of course, it is also possible to have closure devices for all tunnel and channel mouths which would be closable to, for example, reduce the watercraft's resistance during normal forward or backward travel.
A compact construction is obtained by locating the tunnels closely together.
When space is of a premium in the watercraft and costs are also a factor, the compensating channel or channels can be positioned between the tunnels and be free of any associated closure device and, as a result, would function independent of the direction of travel of the watercraft because the tunnel which is the frontmost one would be normally utilized while the tunnel which lies therebehind can be used either as an additional output or can serve as a stand-by unit.
Further advantages and characteristics of the invention result from the following description.